Waste foundry sand contains a binder, such as clay or organic binders such as furan, urethane and the like. The disposal of foundry sand has become a serious problem. Solid waste disposal sites are disappearing and the cost of shipping the foundry sand has increased. Further, on-site disposal is not an alternative because of the environmental regulations and, in most instances, the lack of adequate space for on-site disposal.
Because of this, waste foundry sand reclamation systems have been proposed. In one system the waste foundry sand is fed into the upper end of an inclined rotary drum and air is supplied to the down-stream end of the drum and flows countercurrently to the flow of the sand. Heat is applied to the external surface of the drum to heat the sand to a temperature in the range of about 1200.degree.-1600.degree. F. The heating in the presence of oxygen acts to burn the organic materials from the sand and calcine the mineral additives.
In the reclamation system, as used in the past, the treated sand is discharged from the low end of the inclined drum and flows through a chute to a cooling drum where air is passed countercurrently to the flow of sand to cool the sand. The sand discharged from the cooling drum then passes through a sand scrubber and classifier to remove the fines from the reclaimed sand.
In the prior reclamation systems, the gases discharged from the upstream end of the drum are not completely combusted. Therefore, an afterburner is employed to receive the gases from the upper end of the inclined drum and provide complete combustion of the combustibles. The afterburner is costly and can contribute up to 40% of the overall cost of the reclamation system.